1. Field of the Invention
The present invention relates to material spreading systems, and more particularly, to systems which include a spreader that is translated above the surface of a plastic material which cannot support the spreader.
2. Description of the Prior Art
A variety of different types of floor hardeners have for many years been applied to the plastic surface of uncured concrete. Metallic aggregate is a very finely divided hardener consisting of iron filings. Mineral aggregate hardener (quartz) consists of particulate minerals similar in size to commercially available lawn and garden fertilizer. Traprock and emery rock are floor hardeners having the largest particular size. Miscellaneous other materials are occasionally used as floor hardeners. Each of these floor hardeners is comparatively expensive and may typically cost on the order of twenty cents per pound.
Job application specifications relating to floor hardeners typically state the required coverage density in pounds of floor hardener per square foot of floor surface area. Metallic and quartz aggregate floor hardeners are normally mixed with cement and plasticizers, prebagged, and applied by hand using buckets and wheelbarrows to transport the floor hardener around the job site. Traprock and emery rock floor hardeners are usually hauled in bulk to the job site, transported to the immediate vicinity of the job site by a wheelbarrow and spread over the plastic concrete surface with a shovel.
Application of floor hardener materials by hand or with a shovel requires a great deal of skill and is typically possible only on relatively narrow concrete pour widths. Even skilled construction workers cannot achieve a uniform application rate or a high production rate when working with the floor hardener materials described above.
As a result of the uneven distribution achieved by manual application techniques, a significant excess amount of floor hardener must be applied to the plastic concrete surface to assure that the specified minimum application density is achieved. As a result of the high purchase cost of floor hardener materials, it has been well known for many years that a significant cost reduction in both labor and materials could be achieved if floor hardener materials could be distributed at a high rate and with a uniform application density. A reduction of only one tenth of a pound of floor hardener per square foot of floor area can achieve a significant cost savings and a resulting profit increase, but has been extremely difficult to achieve in practice using prior art techniques.
In the past, a very limited number of contractors have attempted to overcome the shortcomings resulting from manual application of floor hardeners by conducting experiments with domestic lawn spreader equipment. A Scotts lawn spreader having a slotted, manually actuated gate has been used in combination with a dual work bridge or saw horses and a pair of spaced apart planks in an attempt to apply a mineral aggregate floor hardener to a plastic concrete surface. Lawn spreaders were not suitable for use with metallic aggregate since the small size of iron filing particles were incompatible with the lawn spreader mixing and metering systems. The larger size aggregate particles of traprock and emery rock aggregate wedged between the lawn spreader agitator and hopper and jammed in the slotted gate, rendering the device inoperative. Since mineral aggregate floor hardener was similar in consistency to typical lawn fertilizer, only that specific type of floor hardener could be made to function on a rudimentary basis and on very limited pour widths with the Scotts lawn spreader. Because the mineral aggregate particles were dispensed through the spaced apart, slotted apertures in the lower portion of the lawn spreader hopper, the floor hardener material was distributed in spaced apart rivulets, rather than the desired uniform particulate blanket. Numerous difficulties were encountered with steering and manually propelling the two wheel lawn spreader device along the dual work bridge or wooden planks.
These sporadic efforts to distribute even mineral aggregate floor hardeners with a lawn spreader were considered unsatisfactory and were never adopted by the industry.
The prior art includes a variety of different types of material spreaders. U.S. Pat. No. 2,806,435 (Mundell) discloses a suspended refuse spreader which includes a hopper translatable along the length of a pair of fixed, overhead rails. The hopper of this spreader hangs below these fixed support rails and includes a plow-like deflector which deflects the refuse into two spaced apart piles as the spreader is translated along the rails. A cable is attached to one end of the spreader to translate the spreader with respect to the supporting rails.
U.S. Pat. No. 2,807,234 (Middlen) discloses an engine-driven livestock feeding apparatus which can be translated along a pair of fixed rails between which a livestock feed trough is positioned. The material discharged from the lower portion of this apparatus is separated by a deflector within the trough into two heaps so that cattle on both sides of the rail system can be fed.
U.S. Pat. No. 1,200,393 (Neller) discloses an overhead carrier which is translated along a single fixed overhead rail. When the carrier reaches the desired unloading position, the hopper of the carrier is tilted sideways to discharge the contents.
U.S. Pat. No. 3,230,845 (Mauldin) discloses a spreader which rolls over and is supported by the surface upon which material is to be spread. U.S. Pat. No. 3,453,988 (Trent) discloses a portable spreader which is linearly translatable along the length of a pair of fixed rails.
U.S. Pat. No. 2,113,503 (Belkesley) discloses a multiple-purpose spreader which includes a hopper supported by a grouping of three wheels. This topping spreader rolls over the area upon which material is to be discharged.
U.S. Pat. No. 2,318,064 (Delaney) discloses a conventional fertilizer spreader which includes a hopper and a finger agitator rotated by the spreader wheels. A mechanically actuated gate is positioned in the lower portion of the hopper and meters the discharge of material from the spreader.